In order to staple sheets of paper, a general stapler strongly presses and clamps the sheets of paper between a stapling table and a unit for driving a staple. After this state is fixed, a staple is driven so as to penetrate the sheets of paper, and each leg of the staple is then clinched by a clincher.
Such a lock mechanism has been disclosed in JP-B2-2688114, for example.
As shown in FIG. 4 of JP-B2-2688114, a fixing pin 39 is engaged with a bow-shaped slot 38 of a fixing plate 36 and the diameter of curvature of the slot 38 increases, thereby causing a wedge action between the wall of the slot 38 and the fixing pin 39. Such a wedge action fixes a stapler head 12 in an operation position so as not to be vibrated up and down by a rotation of a rotating pin 13.
However, since a frictional resistance between a wall of the slot 38 and the fixing pin 39 is significantly large when the wedge action occurs between them, plenty of energy is needed to rotate the fixing plate 36 in the original position after the fixing. Therefore, when the fixing plate 36 is rotated by a force of a spring, a strong spring is needed, and when the fixing plate 36 is rotated by electricity, much electric power is needed.